Real-time spectrum analyzers such as the RSA6100 and RSA3400 families available from Tektronix, Inc. of Beaverton, Oreg. trigger on, capture, and analyze RF signals in real-time. These instruments capture seamless blocks of data so that, unlike conventional frequency swept spectrum analyzers, no data is missed or lost.
These instruments have what is known as a power trigger or intermediate frequency (IF) level trigger. The power trigger calculates the power of real-time data provided by the instrument's receiver system and then compares it to a trigger level. When the power violates the trigger level, a trigger signal is generated which causes a seamless block of data representing the received RF signal to be stored containing the triggering event as well what happened immediately before and immediately after the triggering event.